High speed rotary flying shear



w. w. MACFARRE'N HIGH SPEED ROTARY FLYING SHEAR Feb. 24, 1942.

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HIGH SPEED ROTARY FLYING" SHEAR I 7 Filed April 10, 1936 10 SheetsSheet 2 INVENTOR.

Feb. 24, 1942. w. w. MACFARREN 2,274,452

' HIGH SPEED ROTARY FLYING SHEAR Filed April 10, 1936 10' Sheets-Sheet 3 INVENTOR.

Feb. 24, 1942. w. w. MAC FARR EN 2,274,452

HIGH SPEED ROTARY FLYING SHEAR Filed April 10, 1936 10 Sheets-SheetA L/J i /33 /30 /29 /20 //2 .66 5- 67 I I v 74' 76 :2 7/

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Feb. 24, 1942,. w. W/MACFARREN Q 2,274,452

I HIGH SPEED ROTARY FLYING SILIEAR Filed April 10,1936 7 1o S heets-Sheet 5- r v V me INVENTOR.

7 Feb. 24,1942. w. w. MACFARREN HIGH SPEED ROTARY FLYING SHEAR Filed April 10, 1936 l0 Sheets-Sheet Z m. I3. m. 14.

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Feb. 24, 1942. w, w. MAcFA REN' 2,274,452

HIGH [SPEED ROTARY FLYING swam Filed April 10, 1936 10 Sheets-Sheet a INVENTOR.

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men SPEED ROTARY FLYING SHEAR 1O Sheets-Sheet 9 Filed April 10, 1936 NWM \Wm wwm Rm Gm wwm m mm wmm mmm M \wm \mm INVENTOR.

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I HIGH SPEED ROTARY FLYING SHEAR Filed April 10', ,1956- l0 Sheets-Sheet l0 I INVENTOR. 3 7 7 Patented Feb. 24, 1942 UNITED STATES PATENT OFF ICE HIGH SPEED ROTARY FLYING SHEAR.

Walter W. Macfarren, Los Angeles, Calif. Application April 10, 1936, Serial No. 73,790

84 Claims.

My invention relates to flying shears for cutting metal bars in endwise motion into desired sectional lengths; and more particularly to rotary flying shears for operating upon bars directly as they come from a hot mill-at speeds from,

2500 to 4000 feet per minute, or more.

Such flying shears offer a great saving in the initial and operating costs of so called hot strip mills, The present tendency in the building of such mills is to make them wider as new mills are built, for the purpose of passing a greater tonnage through them at present mill speeds, which I believe, are as a maximum, about 1000 feet per minute for the larger mills, and up to also the product of these mills is usually subdivided in subsequent manufacture, so that increased width is not an advantage per se.

The present inventor believes therefore, that much higher speeds may be looked for in the smaller mills in order to economize in manue facture; it is obvious that the same tonnage can be rolled on a mill 30 inches wide 2000 feet per minute, as on a mill 60 inchw wide 1000 feet per minute, and with a much less investment in the mill itself, and probably with more reliable operation. The shear of the present invention is therefore designed to suit this coming need.

In my issued Patent No. 1,965,523 for Rotary flying shears I have shown a machine having independently operatable multiple shear knives, spaced for illustration, about two feet apart (pitch) In the said application I have also shown means for angularly advancing the shear knives and their carriers between cuts, in order to make cuts of a length intermediate of even multiples of the knife pitch.

In my issued Patent No. 1,849,501 I have shown a still more refined mechanism for controlling such angular advance of the knives between cuts, which enables the machine to cut in set lengths, including a range sub-divisable into small fractions of an inch, plus a desired base length, as 11'-6} or 19-8 or 274%".'

In my issued Patent No. 1,994,107 I have shown means for synchronizing the circumferential speed of the shear knives with the lineal speed of the bar being cut, in such a manner as to producepractically exact relations between thesespeeds.

Also, it is common practice in the art, with certain types of rotary flying shears, and for lack of better ways as above indicated, to use a shear having one or more rigid knives, and to produce a wide speed differential between the bar and the knives to vary the lengths cut, either by varying (holding back) the speed of the bar, or (more usually) by varying the speed of the shear knives by the use of elliptic gears or similar mechanism, to produce a loaflng range of the knives between cuts, while at the same time obtaining some degree of speed equality between the bar and the knives at the instant of cutting.

In this method, if the speed differential is small the length variation of the cut sections is also small, and if, to enable the shear to cut a variety of lengths, the speed differential is large, the apparatus operates with shock and damage to itself, and'makes cut edges which are ragged and of inferior quality, to say nothing of the inaccurate lengths of the cut sections.

In the application last above referred to I obviate this dimculty almost entirely at present mill speeds, by providing means (choice of which knife shall out) which limits the angular adjustment necessary to make in between cuts to a small amount, and which provides exact synchronization at the instant of cutting.

However, even in this improved construction there are two limitations as to high speed:

1. The first and lesser one is the inertia of the radially adjustable knives and their connectedparts (to cut or not to cut). Subject to this limitation only, shears of medium size can probably be built to cut bars moving at 3000 feet per minute direct from the mill rolls. Such cuts would be in steps," or multiples of the knife pitch.

2. However when cuts of a length in between these steps are required, it is necessary to angularly shift the knife carriers between cuts as before indicated, and as the masses to be moved are in this case greater than thatof the knives and attached parts, and the degree of movement is also greater, the inertia forces to be overcome may become several times as large, and this speed limitation is thus more serious.

The avoidance of this diificulty and the attainment of extremely high cutting speeds is the purpose of the present invention. Suppose we had a rotary flying shearcomprising two parallel rotary members mounted on fixed centers,

'A 10' cut section would become 11- .A 25' 0" cut section would become 27' livery speed) could reach 5000 feet per minute,

for thin material (say up to thick) 'without distress to a properly designed shear; or, in other words, it would probably be practical to shear such a bar at such a speed.

When, however, selective knives are used with a radial adjustment of say (to cut or not to cut) the speed of the bar which may be cut depends on the facility with which such knives can be so adjusted.

If we assume that there are ten knives on each knife carrier, equally spaced around the circumference thereof and of one foot pitch, then the circumferential travel of the knives would be 10 feet per revolution of their carriers, and at 300 revolutions per minute of the said carriers the shear could cut a bar moving at 3000 feet per minute, into sections varying by steps of one foot, or say as a practical example, into sections of from 10 to 30 feet, varying by one foot.

As there is nearly a whole revolution available for the radial adjustment of the knives, at 300 R. P. M. there would be available for this purpose a little less than /5 of'a second, which is within the ability of electric magnets or compressed air cylinders to effect, with proper design.

Now, while a large speed differential between the bar and the .knives is distinctly bad as previously set forth (I believe such differentials exceeding 100% have been used), a small speed difierence at the instant of cutting, under certain conditions (preferably an excess of bar speed over the knife speed, rather than the opposite) might, and probably would, do no practical harm.

Icannot say just what the amount of such a speed diiferential can be, as this is a problem best solved by empirical data obtained from actual experience with machines of this type. In any case the exact amount or degree, of speed variation permissable, is not a matter of concern to us at this moment, as it is certain that tliese" speeds may be asynchronous to some degree, and to whatever extent good practice may set a limit, that value may be taken advantage of by the method and means included in the following disclosure of my present invention.

I will assume for purposes of illustration only, that with the high bar speeds contemplated by the present invention (2500 to 4000 feet per minute), aspeed differential of may be used, or to apply this-to our concrete example, with a ten knife, shear drum of ten feet circumference,

rotating at 300R. P. M. or at a speed of 3000 feet per minute, the bars may be fed to it and successfully sheared, at lineal bar speeds up to 3300 feet per minute.

The effect of this would be to increase the length of a normal cut made at equal speeds, as follows:

0 long 6" long 0". long A 0" cut section would become 16' A 20' 0" cut section would become 22.

A 0" cut section would become 33' 6." long 0" long operation of the bar and knives at a'speed differential up to 10%, the length of the cut sections can be accurately controlled for in between cuts, without any other speed limitation than the time required to radially shift the comparitively light shear knives and attached parts, to cut or not to cut.

In this sense, and for these extreme high speeds, this is an improvement on my previous inventions above referred to. It will now be seen that for any length of out over 11 0", a 10% speed differential is more than enough. For I It will also be obvious, that with suitable adjustable mechanism to accurately control the asynchronism, it is easy. to compute the precise amount of asynchronism required to produce any desired cut length, in units of feet, inches, and inch fractions, so that by such mechanism taken H as a whole, any desired lengths may be cut.

The steps required to produce such apparatus are as follows:

1. Determine by experience or tests the degree of asynchronism practically permissable at the desired speed and for the given material.

2. Provide a shear having evenly spaced knives,

independently operatable in desired sequences,

' the synchronous pinch rolls, the asynchronous pinch rolls, and the connecting drives.

Fig. 2 is a diagrammatic side elevation of a strip mill, a rotary flying shear according to the present invention, an approach table, and piling tables.

Fig. 3 is an elevation of the operator's end of the shear.

Fig. 4 is a longitudinal vertical section of the shear proper, exclusive of the drive and controls.

Fig. 5, is a vertical cross section of trunnion 29 and connected parts.

Fig. 6 is a similarview of trunnion 30 and connected parts.

Fig. '7 is a vertical cross section through an up'per and lower co-acting shear kmfe, showing the mounting of the same in the carrying drums, and taken on the line 1-1 of Fig. 4.

Fig. 8 is a vertical cross section through one 'of the knife oscillating air cylinders and connectedparts. on the line 8- 8 of Fig. 4.

In other words, by combining a number of selectively operatable knives, closely pitched,

Fig. 9 is a cross section of thetake-up for the control chains, takenon line 99"of Fig. 3.

Fig. 10 is a cross section through one end of a lower drum trunnion on line I 0l0 of Fig. 3. Fig. 11 is an end elevation of the trunnion for the upper drum, and its valve plate, showing the air ports for the distributing .valve.

system.

Fig. 18 is a plan of a portion of a control chain, and Fig. 19 is an elevation of the same.

Fig. 20 is a view' partlyin vertical section, of

a modified form of pinch rolls wherein their diameters are controlled by temperature changing means.

Fig. 21 is a partial longitudinal vertical section of the machine, similar to the right half of Fig. 4, and showing a modified arrangement of drum connecting gears.

In my previous applications Ihave shown and described electric magnets for the radial adjustment of the knives, and various electrical controlling devices in connection. 1

Electric magnets have marked advantages and marked disadvantages for such service. Among the disadvantages are 1. The danger of short circuits.

2. Their increased weight, size, and cost over other available mechanism.

3. The time necessary to energize and deenergize them.

4. The fact that apparatus of this kind is almost invariably built by a machine shop,- and by using mechanical devices only the maker reduces his purchases of outside material, and keeps his profits at home. v

5. Mechanical defects are usually more obvious.

For these reasons, especially the 2nd and 3rd I prefer to make use of air operated devices for adjusting the shear knives, and as far as possible, mechanically operated controls for the said other. The boxes 5 rest in a window I between.

the side posts 3 of the housings 2 and 3.

The lower boxes 5 rest on surfaces 3, and the upper boxes 5 rest on separators 6. Shims I may be placed between the upper boxes and the separators 6 for accurate adjustment.

The tops of the housings 2 and 3 are closed by caps I] and .4, which may be secured by bolts I2 having cotters l3, all in the usual manner. Mounted in the lower boxes 5 there is a lower knife carrier or drum- I4, and similarly, in the upper boxes 5 there is mounted an upper knife carrying drum l5.

The lower drum I4 is provided with hollow trunnions I6 and I1, upon which are mounted the inner races N of roller bearings, which also include the outer races l3 and the rollers 20.

'The' trunnion I8 is bored to receive astub end 2| having alflange 22 which may be secured to the end of the trunnion IS. The member'2l :ls 3

also provided with a pod 23 or other suitdble connection for a drive spindle.

of my improved rotary flying The trunnion I3 is enlarged at 24: to form a seat for the drive gear 25. which is a one piecegear having double helical teeth, the teeth on .the two sides of the gear being designated 23 and '21, and having preferably a helical angle of about degrees.

The trunnion I1 is also bored to receive a member 28 which will be described later, as will also the knives and slots for the same in the lower drum [4.

The upper drum I5 is provided with trunnions 29 and 30 upon which similar or duplicate roller bearings may be mounted. Unless for unusual reasons the four main roller bearings for the drum trunnions would be duplicates.

The trunnion 33 is enlarged to, form a seat 3l' for a pair of gears 32 and 33, placed back to back, and bolted together by bolts 35 against the shims 31. The inner gear (half) 32 has helical teeth, which mesh with the teeth 25 of gear 25., The outer gear 33 has teeth 35,

which mesh withthe teeth 21 of gear 25.

If the two gears 32 and 33 have oppositely vslanted helical teeth as shown, they are, for

The reason for splitting the 'upper gear 3233 is as follows:

In shears of this type, the cutting knives on the two drums I4 and I5 must be accurately registered, and this is accomplished, first, by

mounting the drums in accurate bearings; and

second, by connecting the drums by accurate gears. By present practices machine cut gears of minute accuracy as to tooth form and tooth spacing are produced as a commercial product,

and in this machine usual commercial accuracy is all that is required, as the gears 3233 and 25 are of even ratio, with an equal number of teeth; consequently the same teeth are in contact for each cutting position of a'pair of coacting knives.

With new gears, the center distance between the drums I4 and I5 can be accurately adjusted by the liners l0, and the backlash" can be reduced to a minimum.- However, as the gear teeth 26, 21, 34, 35 wear, this backlash will increase, and affect the accurate registry of the knives.

However the evil eifects of backlash are not so evident except when. cutting thin material.-

If the shear is used to cut hot skelp an inch thick, of backlash might have no perceptible ill eifect, although of course it would do no good. If however, the shear was used to cut strip steel only thick, 1% of backlash, or even much' less, might destroy the ability of the shear to make clean cuts, as the strip could wedge itself between the coacting knives without being cut at all.

When cutting thick stock'the construction shown in Figs. 1 and 4, of double helical gears with the usual opposed helix angles is practicable. In this case the gears'can be initially set to reduce the backlash to a minimum, and

'thusdra ing ,the drums I l and I5 and their gears closer together. It is-however, desirable tohave aspecial adjustmentto control the backlash, and one with a greater range of adjustment. This can be done as follows:

With gear teeth 23, 21, 34, and 35 of opposed helix angles as shown in Fig. 4, if the shims 31 are reduced or increased in thickness, the Bear teeth 35 may be moved to right or left :as the case may be, or in effect the teeth 34 and 35 are brought closer together, or spread farther apart, while the teeth 23 and 21 are unchanged. This action will merely change the angular relation of the drums I4 and i5, as they are free to rotate. However, if the helix angles of the teeth 23 i and 21 are the same with reference to the drum l4, these teeth being in a sense parallel instead of opposed as shown in Fig. 4, then as the teeth 35 are moved along the shaft with reference to the main driving forces from the similar pair of the teeth 34, by changing the thickness of the shims 31, and if the drums l4 and I5 are fixed endwise in their bearings; the teeth 34 will tend to hold the teeth 23 against rotation, while the teeth 35 will tend to rotate the teeth 21 in one direction, thus eliminating backlash to any desired degree. This is the object of the construction shown in Fig. 4 for axially adjusting the gear 33' and the teeth 35 by the shims 31 and the bolts 33. In this case there will be end thrust between the drums l4 and i5 which may be provided for in any usual or preferred way.- This thrust is to, some extent neutralized by the frictional contact of the knives and the stock.

Also, in this case, as the machine runs in one direction only, the meshing teeth 26 and 34, or the meshing teeth 21 and 35 will do the actual driving, the other set of teeth being used to control the backlash. The widths or faces of these two sets of teeth can be proportioned for their respective duties.

The arrangement above described for eliminating backlash is effective for that purpose, but it introduces end thrust in the drum drive which is objectionable. In order to eliminate this end thrust and secure the advantages of the double helical drive shown in Figs. 1 and 4,

I show a third arrangement of gears in Fig. 21, consisting of six gears arranged as follows:

On the upper trunnion 30 there are three gears 313, 3H, and 312, set side by side. The left gear 313 is a single helical gear loosely mounted'on the seat 3| for axia-l adjustment, and may be practically a duplicate of the gear 32 of Fig. 4. The middle gear 31! is a spur gear (straight teeth) of equal diameter and pitch to ia'l'ie gear 310, and may be a press fit on the seat The right gear 312 is a single helical gear of the same size as the gear 313, but having teeth of the opposite slope, and may be practically a duplicate of the gear 33 of Figs-4, and is loosely mounted on the seat 3i for axial adjustment.

All three of the gears 313, 31l, and 312, engage the key 314. Between the gears 310 and 31l, and between the gears 3H and 312, there are placed a number of shims 315, and bolts 313 pass through the three gears 310, 311, and 312, and th shims 315 to lock them together.

, On the seat 24 of the trunnion l3 there are placed three similar gears 311, 313, and 319, the helical gear 311 meshing with the helical gear 310; the spur gear 313 meshing with the spur gear 3H; and the helical gear 313 meshing with the helical gear 312.

All the gears 311,313, and 313 may be a press fit on the seat 24,:and 'be engaged by the key 383.

The gears 3,10 and 312 being of opposite hand. form in effecta double helical gear'whlch takes gears 311 and 313, and the meshing spur gears 3H and 313 serve to control the backlash. When the shims .315 are removed and replaced by thinner shims, the gears 313 and 312 may be drawn closer together by the bolts 313, thus rotating the upper drum i5 an amount suilicient to assure close contact between the teeth of the spur gears 31 I and 318.

This arrangement gives all the advantages of the simple double helical drive as shown in Figs. 1 and 4, with the ability to reduce the backlash to any desired amount, and by subsequent adjustments to so maintain it during the entire life of the gears.

I may now state that I prefer to mount the lower drum I4 in its bearings so that it is fixed against endwise motion, and I prefer to mount the upper drum l5 to float endwise a small amount, say its position endwise being determined by the mesh of the helical gear teeth 23, 21, 34, and 35.

I will now describe the mounting of the shear knives in their drums. Since, in order to. adjust certain of the knives to cut, or not to cut," either half or all of the knives must be adjustable. I prefer, for cutting thin material such as strip steel, to make only half the knives so adjustable,-to simplify the construction.

This being decided, a further decision is necessary. All the adjustable knives may be placed on one drum, and all the fixed or rigid knives on the other drum, or half of each kindof knives may be placed on each drum.

In prior applications hereinbeiore mentioned I have used the latter method, but in the present invention I prefer, for reasons which will appear later, to place all the adjustable knives on the upper drum l5, and all the fixed knives on the lower drum i4.

Referring to Figs. 4 and 7, the lower drum i4 is provided with a series of evenly spaced slots 38 (in the present discussion there are ten of these) having two parallel sides 39 ,and 43. Each slot 38 connects with a small bored hole 4| formed in the drum I4 parallel with its axis, the lower portion of which forms a seat for a knife. A rib 42 extends parallel to the "slot 33, and set screws 43 are set therein to hold the knife; wrench clearance being provided by the space 44, which may be subdivided by ribs 45.

Flat shims 41 are provided for lining the knives horizontally (as shown in Fig. 7), and curved shims '43 are provided for setting the knives to correct radial position.

The knives 53 have parallel sides 5! and 52, a lcwer oval shaped portion 53, a curvedupper face 54, and a single cutting edge 55. These are the rigid knives, being held in operative position by theset screws 43, and adjusted for position by the shims 41 and 48.

The oval portion 53 is wider'than the slot 38, so that if the set screws 43 work loose, the knife 53 cannot be thrown out of the slot 38 by centrifugal force. In placing and removing these knives in and from their slots, they are moved endwise. a cored opening 56 being formed in one of the separators 6 for this purposes. (See Figs. 3 and 4.)

The lower drum M has a continuous outer barrel 51 connected by the end pieces 53 and having an inner barrel 82, end members 88, ribs .64, and an outer barrel 85. In the drum I8 there are formed small barrels .68 in which are formed bored holes 81, in each of which is mounted an oscillating knife holder 88, having a slot 88, in which is placed an upper oscillating knife I8.

The slot 88 joins a small bore II, formed to receive the oval edge 12 of the knife I8, and the shims I3. same in all dimensions as the lower knives 58, except as to their width (vertical in Fig. '7) which is greater. As the knives I8 are worn and ground down, they become too narrow for use in the knife holder 68, andcan then be used as *relation to the cutting edge I8 of the upper knife I8, when the said upper knife I8 is pressed against the lip I8 of the drum I5.

A second lip 88 is formed in the drum I5, there being an open space between the lips I8 and 88, so as to clear the oscillating swing of the knife I8, which moves from the cutting position against the lip I8, to the normal inoperative position as indicated in dotted lines at 8|. Wrench clearance for the set screws I8 is furnished by appropriatenotches 82.

It will be observed that the cutting edge I8 of the knife I8 is located on the center line of the bore 81, and as the cutting pressure on the knife I8 is always to the right of the cutting edge I8, the tendency of the cutting pressure is to force the knife I8 closely against the lip I8, thus giv- The upper knives 18' maybe themounted on fiat seats 88 formed on the trunnion v 28, and in Fig. 8 I have shown one of the air cylinders 85 in section, and its relation to adjacent cylinders. All the cylinders 85 are duplicates.

Each cylinder 85 is formed in two parts, a base section 81, and a cover section 88. These two sections are joined by flanges 89, andv bolts 83.

ing extreme rigidity to the knife at the instant It will be understood that the knife holders 88 and the bores 81 are accurately machined and smoothed to an easy. working fit, so that the knife holders may be quickly oscillated when desired. It will also be noted, that due to the small diameter of the knife holder 88, and to its oscillating motions, its inertia is low.

It will also be noted that the above described adjustment of the oscillating knives, to cut or not to cut, is to all effects and purposes a radial adjustment, although the path of the knife is not strictly on a radius of the drum, its cutting edge is withdrawn to a lesser radius, and so cannot engage the material to be cut. The side shift of the cutting edge has no material effect, itbeing used merely as a matter of mechanicalconvenience.

' ing 2 is provided with a similar cap II,. secured Attention is also called to the fact that the v drums I4 and I5 are simple in form, and comparitively easy to produce as steel castings, and that the machining operations required are simple and of ordinary character, such as may be performed in any well equipped machine shop. This also applies to the knife holders 68,

which are preferably made of rolled or forged steel. It will be understood that all the knife holders 68 are duplicates, as are also the bores 81, the knives 58, the knives I8, the slots 38, and the slots 88. P

A piston 88 works in the cylinder 85, and is provided with a pressure end 8I having a boss 82 which abuts on the surface 86; a set of spring rings 83, a shoulder 84, a wrist pin 85, and an extension or guiding portion 88 which worlm in the bore 81. The piston 98 is preferably hollow as shown.

A coiled spring 88 surrounds the guide portion 86, and is confined endwise between the shoulder 84 and the inner surface 88 of the cylinder section 88. Compressed air to operate the piston 88 is supplied through an air port I88 drilled in the trunnion 28. It will be understood that the air pressure in cylinder 85'positions its corre- .sponding knife I8 to cut, as shown in Fig. 7, and

which is connected to a pin I83 mounted in the end of a lever I84, the said lever having a noncircular opening fitting over the end I85 of the knife holder 88 to oscillate the same. (See Fig. 8.) The air cylinder 85 is secured to the-seat 88 by lugs I88 on the base section 81, and bolts I8I. Thin copper base gaskets may be used.

It will be observed from Fig. 8 that the air cylinders 85 are spaced on radial lines bisecting the angle between two of the oscillating knife holders 88.

As shown in Figs. 3 and 4,'the housing 3 is provided with a cap 4 secured by bolts I2. The housby similar bolts I2, and also provided with a cored opening II8, through which the upper knives I8 may be successively removed and replaced by rotation of the drum I5. The opening II8 also serves to withdraw and insert'the oscillating knife holders 68, when necessary for inspection and lubrication. With a simple grinding attachment all the knives may be ground in place.

It will also be apparent that the knives I8 may be changed when dull by removing'the knife holders 88 with their contained knives I8, and substituting other knives on the bench; in fact if this practice is followed time is saved.

To supply compressed air to operate'the air cylinders 85, I provide a rotary ported distributing valve H5 as shown-in Figs. 3, 4, 11, and 12, T

.sists of a port box" or-rotating member 2-,

makes an air tight joint against the flat end of trunnion 29, and a fiat working face or seat H8. Between the two faces H8 and H1 there is formed in the member H2, a series of radially disposed evenly spaced air ports H8, one for each air cylinder 85. The ports H8 may be made of greater volume by increasing the size of the member H2 in diameter or length.

At the face H1 the ports H8 connect with the drilled ports I in the trunnion 29, which supply the cylinders 85. As shown in Fig. 5, the valve seat H8 iscovered by a distributor plate H9 having a flat surface or seat I2 I, which bears against the face H8 of the member H2, and covers all the ports H8. The plate H9 is pressed against the seat H8 by a spring I08.

The member H8 has an integral cylindrical stem I22, which slides freely in a close fitting guide I23, formed in a bracket I24 secured by' bolts I25 to the cover plate I28 of-the bearing .box 5. Keys I21, secured to member I I8, prevent rotation thereof by engaging the keyway I28 in the bracket I24. It is obvious that the angular position of keyway I28 and keys I21 is so chosen as to obtain the proper registry of the valve ports H8 with the supply and exhaust ports I34 and I52 in member H9.

The housing for the supply valve I20 may be formed integral with the member H9, and provided with a grooved seat I29 on which the gridiron supply valve I30 operates. provided with a tapped opening I32 for a flexible air conductor I33 to supply compressed air.

The valve I20 is provided with a twisted port I34, its outer end connecting with the series of small ports I35 beneath the valve I30, which has matching ports I38 extending through it. The inner of the port I34, where it meets the valve seat H8, is the shape of the radial ports H8, and matches with them.

The valve I30 is operated by a rod I40, which passes through a stuiling box I4I having the adjustable gland I42, and is held normally in the closed position as shown in Fig. 12 by a coiled spring I43 acting against the washer I44. The end motion of valve I30 is limited by the end I48 striking the surface I41.

The outer end of the rod I 40 is engaged by a guide I49, and its end may be engaged by a lever II carried by a rock shaft I50. From the foregoing it will be apparent that by the intermittent operation of the lever I5I the gridiron air supply valve will admit airto one of the ports H8, and'that this air will pass through one of the ports I00 to one of the air cylinders 85, to position one of the oscillating knives to cut when it next meets its co-acting rigid knife 50.

This quantity of compressed air will be supplied when one of the rotating ports I I8 is at the position A" in Fig. 11, and will, when the port H8 rotates out of line with port I34, be bottledup in the ports H8 and I 00, and the cylinder 85. 7

Due to the high speed of rotation of the drums I4 and I5, it is-probable that no adjustment of the oscillating knife holder 88 will take place un- A cover I3I is til' the ports H8and [34 are out of register, so

that all the work of moving the piston 90 will tion of the knife holder 88 will be a little less than A of a second. The required air pressure will depend on the friction and inertia of the knife holder 88 and its connected parts, and the required unit air pressure will also be a function of the diameter of the cylinder 85. In addition, it must be taken into account that the air works expansively, and must, at the outer end of the piston stroke (90), have suillcient available force to hold-the knife 10 closely against the lip 19, and against the pressure of the spring 98; and in addition an excess amount of air must be supplied to compensate for leakage past the rotary distributing valve H5, and the piston rings 93 of cylinder 85.

In other words, a suflicient amount of compressed air must be rammed in to accomplish these results with certainty. With ten ports H8 as shown in Fig. 11, having a maximum width at their outer ends of 1 A", and operating against a similar port I34 of equal'dimension, the air would flow during 2 of travel of the outer port circumference which is, as shown, about 33".

The ports H8 and I34 would be partially open or connected for or .0757 revolution, or about 27 degrees. At 0.2 second per revolution (300 R. P. M.) the time of partial opening would be 0.2 .075'7, or 0.1514 second, to pass compressed air at say, 100 to pounds pressure.

As a fluid speed comparison, the gas is drawn by suction (2 to 3 lbs. vacuum) into the cylinder of an automobile motor 3000 R. P. M. at the rate of a cylinder charge (one whole stroke) in 36 minute or ,5 second. So the above design allows 50% more time to move a smaller amount of air at a pressure about fifty times as great.

I now come to the consideration of the necessary timing of -the air supply to the cylinders 85 in order to make the desired cuts, and I will first discuss this for an exact synchronous relation between the linear travel of the bar to be cut and the peripheral travel of the shear knives.

It is obvious that with the apparatus so far described to make 10 ft. cuts, it will be necessary to cause each 10th knife to cut, and to out. 30 ft. sections it will be necessary to have each 30th knife make a cut.

In addition to this it will be desirable to cut a short and predetermined crop end off the front end of each bar.

To these ends, I have shown in Figs. 3, 10, and

15, certain mechanism, as follows:

The trunnion I1 has a counterbore I54, to receive a shell 28, having a flange I55 which may be secured to the end of thetrunnion. The shell 28 supports a short shaft I56, secured by a key I59 and a nut I58. The shaft I58 carries a helical drive pinion I51 mounted on a feather key I51a, and a coiled spring I 80 bears against it as shown.

The outer end of the shaft I58 is threaded, and

carries a nut I8I which may be used to adjust the pinion I53 along the shaft I58.

The slope of the pinion teeth I83 is such that the thrust is taken against the nut I8I.' The pinion I51 drives the mechanism which operates the supply valve I20,-and by adjusting the pinion I51 longitudinally on the shaft 156, a fine angular adjustment is obtained for the control chain I95 which operates the supply valve I20.

The pinion I51 rotates in the direction indicated in Fig. 3, and drives an idler. gear I85 mounted on a fixed pin I66, which may have a flange I 61 bolted to the cover plate I68 of bearing box 5. The gear I65 meshes with and drives a ,helical gear I mounted indirectlyon a shaft fines the clutch I against end motion.

The shaft I1I also carries a brake drum I18 which is engaged by a brake shoe I19, which may be operated by a solenoid magnet I80, against the pressure of a spring I69.

The brake drum I18 is pressed on the shaft I1I andheld by 'a key I8I. Thehub' I82 of the brake drum I18 carries a light jaw clutch member I83 which slides freely on a feather key I84,

and is provided with fifty small clutch teeth I85. The teeth I85 match and mesh with fifty corresponding teeth I86 on the magnetic clutch I15, and the clutch I15 is adapted to draw the clutch member I83 magnetically toward it to engage the teeth I85 with the teeth I86, and against the pressure of the small coil springs I81, acting through the bolts I88.

Contact rings I89 and I90 are furnished to supply current to the magnet coil 49. outer end of the shaft I1I there is mounted a fifty tooth sprocket I 92, keyed to the shaft IN by a key I93. A similar fifty tooth sprocket I94 is loosely mounted on a take-up member I9I (see Fig. 9), which, in turn, is mounted to slide on a bracket I86 which is bolted to the housing 2. The required adjustment is about 12", which will appear later. A rack I91 is fastened to bracket I96, and engaged by a pinion I98, which may be formed integral with the shaft I99 which '()n the I is mounted in the member I9I, and operated by a hand wheel 200 secured to the outer end, of the shaft I99.

A latch pin 20I locks the member I 9| in certain selected positions as will appear later.

Around the sprockets I92 and I94 there is placed a control chain I95. These chains I95 are changeable, and one 'is required for each base length of sections cut. For synchronous cutting of sections 10 ft. to 30 ft. inclusive, there would be a control chain I95 for each length, as for instance 1011-12 28--29-30 ft.

The control chains I95, for this discussion, may be taken as of one inch pitch, with all "offset" links (see Figs. 18 and 19) so that a chain may be put together in any length of even inches.

rock shaft I carries a lever 206 which may be supplied with a roller 201, for engagement with the projections 205.

With other conditions correct, each time the rod I40 is depressed one of the cylinders is supplied with a charge of compressed air, and each time a projection 285 passes the roller 201, the rod I40 is so depressed.

Therefore, if every 10th link of the chain I carries a projection 205 the machine will cut 10 ft. sections, using every 10th knife, and similarly for other lengths of cuts. We may assume that a control chain I95 to cut 10 ft. sections, is composed of 11 sections of 10 links each, with\ every 10th link carrying a projection 205, which is t Then other convenient lengths of control chains I 95 are as follows for cuts 11 ft. to 30 ft.

It will thus be seen that the lengths of the control chains I95 required to make all base length cuts from 10 ft. to 30 'ft. inclusive, and varying by one foot, vary only from 100" to in length, and can be accommodated on the sprockets I92 and I94 with an adjustment of the slide member I9I of about 12".

Referring now to Fig. 16, when the front end of the bar 2I0 to be cut, reaches the adjustable ilag" 2| I, it engages the same'and swings the movable contact 2I2 against the stationary contact 2I3, thus allowing current to flow from the positive main 2I4 via the closed knife switch 2I6 and the wires 2I1, 2I8, and 2l9, to the magnetic switch 220, and thence through the wire 22I to the negative main 2 I 5.

When the switch 220 is energized it raises the arm 222 and carries the contact 223 into contact .with the contact 224, thus allowing current to The ratio between the gears I51 and I10 is one to five, so with the drums I4 and I5 rotating at 300 R. P. M., the shaft HI and sprocket I92 rotate at 60 R. P. M. i

Since with ten knives per drum, at 300 R. P. M.

wthere are 3000 knivespassing a given point per minute, and similarly with the fifty tooth sprocket I92 rotating at 60 R. P. M. there are 3000 sprocket teeth, or 3000 chain links passing a given point per minute.

There is thus a link of the chain I95, moving its length or. one inch, for each knife of .the drum I5 moving one foot. .Thus each link of the chain I95 may be in synchronous relaticn with some one of the oscillating knife holders 68.

Referring now to Figs. 3 and 1-6, the chain I35 carries a number of projections 205. The

flowfrom main 2I4 through wires 225 and 226 to contact 221, and through contact 228 on the hinged arm 229, through wire 230 to wire 2I9,

thus establishing a "hold-on circuit for the magnetic switch 220.

As the arm 222 is raised, it also carries the contact '23I to meet the contact 232, and thus allows current to flow through the wires 233 and 234 to the brush 239 supplying the magnetic clutch I15; after passing through the clutch magnet this circuit is completed by brush 240 and wire I leading to the negative main 2I5.

When the magnetic switch 220 is de-energized. the am 222 falls by gravity, and the contact 223 engages the contact 245 from whence a wire 246 leadsto a contact 235 mounted on one arm 2360f a small bell-crank 242, pivoted by a pin 241 (indirectly) to the bearing bracket I13. (See Fig. 15.)

The contact 235 may swing into engagement with a contact 231 also supported by the bracket I13, and a wire 248 connects the contact 231 with the terminal of the brake magnet I80. This circuit is then completed by the wire 249 leading to the negative main 2I5.

A" vertical arm 250, secured to the arm 236 carries a small roller 25I, which engages the rear side of the shiftable clutch member I83. The

movable contact 235 is therefore operated by the shifting of this clutch member.

When'the magnetic clutch I15 is de-energized, and until the clutch teeth I85 and I85 have been fully disengaged, no current can flow through the brake circuit just described. This arrangement is made to prevent the prior engagement of the brake magnet I80, which might prevent the proper disengagement of the clutch teeth I85 and I85.

The contact 225 is carried by one arm of a small bell crank which is pivoted by a fixed pin 249 over the control chain I95. The arm 244 of the bell crank 242 is arranged to be engaged successively by the chain projections 205 as they pass under it, each projection 205' breaking the hold-on circuit for the magnetic switch 220, but this actiondoes not release the clutch I15 as long as the main circuit to the magnet 220 by the engagement 'of the flag 2 with the bar 2 I0, is closed.

When, however, the rear end of the bar 2I0 passes by and releases the flag 2, then the main circuit to the magnet 220 is broken, and

the clutch I15 is then under the control of the hold-on circuit through contacts 221 and 228.

It is necessary, inorder to limit the length of the front crop end, that the magnetic clutch- I15 be released after the passage through the shear of each rolled bar, and this release is effected by the action of the arm .244.

After the flag controlled circuit is broken, the next projection 205 of the chain I95, breaks the hold-on circuit by separating the contacts 221 and 228.

This action occurs approximately at position A in Fig. 16, and-the brake shoe I19 being then applied, the sprockets I92 and I94, and the chain I95 are brought to rest, with the projection 205 which caused this action, approximately at the position B in'Fig. 16. The distance from A to B represents in movement, of the projection 205, the'time required by the brake I19 to bring th affected parts to rest.

It will now be noted that the end of each cutting cycle (each rolled bar cut up) is thus definitely terminated with one of the projections 205 of the chain I95, at position B," in which position it is ready to quickly start a new cutting cycle by operating the lever 205,- which controls the action of the air supply valve I20. 7

The distance from position B of Fig. 16 to the point where the projection 205 operates the lever 205, is'quite definite for any given setting of the brake, since the-speed of the chain I95 stant for any out section length.

This distance may be assumed as about two pitch lengths' of the chain I95, or equivalent to the movement of two of the knives 10 past a given point, or in other words, as two feet of travel of the bar 2I0.

Assuming now, that we desire a front crop end one foot long, an'd remembering that the selected knife cuts about 9' 0 or nearly a full revolution after its corresponding air cylinder 85 is supplied with compressed air, the adjustable flag 2I I is con-.

set

It will be also apparent that two or more lengths of cut sections (accurate predetermined lengths) may be cut at the same time, from the same bar 2I0, by spacing the projections 205 unevenly on the control chain I95, as for instance, three sections of 25 links, and three sections'of 15 links, to cut 25 ft. and 15 ft. lengths. This may be of advantage to the mill in case the customer desires mixed shipments of two or more lengths. v

It is thus evident that the simple device of a control chain I95, having spaced projections 205, and driven in a fixed ratio to the rotative speed of the knife carriers I4 and I5 for all lengths of cut sections, not only controls the lengths of the said sections, but also the length of the front crop end (its approximate length).

Referring now to Fig. 1, which shows 2. diagrammatic plan view of the shear, a pair of synchronous pinch .rolls, a pair of asynchronous pinch rolls, and the drives for all of this mechanism, the shear, designated as a whole by the numeral 255, sets on the base plate I, which may be extended to also support the motor 255.

The motor 255 is preferably a direct current .shunt wound motor running abo 1200 R. P. M.

and supplied with special speed and torque controls as described in my Patent 1,994,107, for

Synchronizing mechanism for rotary flying shears.

' The motor 255 drives af'short shaft 251 suplower trunnion I5 of the lower drum I4;

' Asbefore mentioned, the drum I4 is 'flxe against endwise motion, the drum I5 is allowed.

to float endwise in its bearings, a small amount, and the shaft 251 is also preferably mounted to permit of a small endwise floating action.

A short shaft 260, mounted in suitable bearings, is connected to and driven by the member 23 from the trunnion I5, through a suitable spindle 25I The shaft 250 carries a bevel gear 252, which meshes with a bevel gear 259 on the shaft 254. The'shaft 254 carries 'a bevel gear "255 which meshes with a bevel gear 255 on a pinion 251, similar to a rolling mill drive pinion.

There may be either two or three pinions 251, forming either a'2 high{ or a "3 high" pinion stand, and in either case. the bevel gear 255 is preferably mounted on the bottom one of the The upper two pinions 251 of the set, if there are 3 pinions, or both of the pinions 251 if there Q are two, drive spindles 259 of which there' are roll 259, of which there are two,

two, and each of the spindles 258 drives a pinch other.

The pinch rolls 259 and their driving members, may be designated as a whole by the numeral 210, and are the synchronous pinch rolls, or those for synchronous operation of the shear knives 50 and 10 (as to peripheral speed) with the bar or strip 2I0 (as to lineal speed).

Since the cutting periphery of the knives is /here assumed to be ten feet, or 120 inches, it is only necessary to make the pinch rolls 259 one third of this or of 40" periphery, and gear them to the knife drums l4 and I5 in the ratio of three to one, as shovm. In other words, if the pinch rolls 259 have a periphery one third that one above the of the drums u and I5, they will have to rotate three times as fast to have an equal peripheral speed.

A secondset of pinch rolls, designated as a whole by the numeral 286 may be inall respects similar to the pinch rolls 216 except as to the diameter of the rolls 215, and may be driven by duplicate gears 21! and 212, pinions 218, and spindles 214.

These are the asynchronous pinch rolls, and are changeable as to the rolls 215 foreach'ac- ,curate cut length required between the "base lengths in even feet, or rather one pair of asynchronous rolls 215 will produce a number of cut section lengths. For instance rolls 215 to cut lengths of .1" will also produce lengths of l 2", 2 3", 4", 5", 60" 67!;70! 7!! 80! 8!! It will now be obvious that since either the rolls 269 or 215 may be changed for others, a' single stand of pinch rolls 216-or 286 might be em-. ployed for both synchronous and asynchronous operation, but I prefer to employ two sets of pinch rolls, one for synchronous operation which is always in place and ready to operate, and one for asynchronous operation whichmay be used only when asynchronous operation is required.

In order to operate the mill continuously, the stand 286 of asynchronous pinch rolls may be picked up bodily and the rolls 215 changed for others, while the synchronous rolls 216 are 8111-,-

ployed to cut stock, or over size lengths in even feet.

If only one stand of pinch rolls, as 216, is used, only 2 high pinions 261will be needed, as the cured in a variety of ways, as by set screws, spot welding, etc. Such sleeves can be re-turned or- 42", and their maximum For the asychronous pinch rolls 215 a similar construction may be used when the rolls are in more or less constant (occasional) use for standard orders of asynchronous length sections.

However, as each accurate asychronous length section cut requires aseparate pair of asynchronous pinch rolls, of a definite and accurate diameter (except as previously noted), I prefer to make the asynchronous pinch rolls 215 in two parts; a standard body portion 295 including the journals 296 and the portion 291 toengage the drive spindles, and a separate outer sleeve 298 which may be made of cast iron, sections of welded steel pipe, or other cheap material for occasional orders, or of hardened steel or bronze for the larger or more frequent orders.

Such sleeves 298, of whatever material, maybe simply pressed on the body portion 295, orsereground several times, to suit different asynchronous section lengths, and then discarded. Also such a pair of sleeves may be quickly prepared for an unusual order. Y

If the synchronous pinch rolls-269 cumference, or about 12%" in diameter, and if the maximum percentage of asynchronization 'used is 5%,. the circumference of the asynchronous pinch rolls 215 would vary from 40" to diameter would be about 13%".

shaft 264 can be slanted vertically to make up opentop housings 216 havingcaps 211, secured by bolts 218; the said housings 216 resting on a bed plate 219, and being secured thereto by bolts The upper of'the two rolls 215 is supported in bearing-bfixes 282 which rest on steps 288 formed in the housing window 284, and are clamped in place by the caps 211.

The lower of the two rolls 215 is mounted in.

bearing boxes 285, which slide freely and are vertically movable in the lower window 286, and are each supported by ahollow piston 281 provided with spring rings 288, and operating in a cylindrical bore 289 formed in the lower portion of the housing 216. Liners 296 may be placed between the bearing boxes 282and 285 to limit the "bite of the pinch rolls 215,

The cylinders 289 may be supplied with compressed air from a pipe 361 as shown in Fig. 17.

As to the construction of the individual pinch rolls 269 and'215, if a separate stand 216 'is exclusively used for synchronous operation, the rolls 269 therefor, are preferably made of hardened-steel or chilled cast iron, and accurately ground to size, unless such material would mar the surface of the strip, in which case soft steel rolls may be used, the same being sheathed in 7 brass or bronze.

It can now be seen that the gears 2H and 212 may be duplicates of the gears 265 and 266, and

the pinions 261 of the pinions 213. It will also be obvious that the asynchronous operation of way from its synchronous operation except that different diameters (or pairs) of pinch rolls ar used.

relation is maintained indefinitely between the lineal speed of the bar being'cut, and the peripheral speed of the revolving knife carriers and their knives 56 and 16. y

It will be further noted, that while I have gle In both cases an accurate and definite speed are 40" cir- 'my improved rotary .fiying shear differs in no q scribed as a concrete example, a shear tocut.

sections from a bar moving at a lineal speed ofv I 3000 ft. per minute, there is no apparent mechanical reason so far evident, why this speed may not be increased to 4000 ft. per minute, or 1 more. i

Since centrifugal forces acting on the knives and their holders have little or no eflect in this design, and since the air cylinders 85, and the air ports H8 and I66, may be-increased in size to permit quicker air flow, and since the inertia of the movable knives 16, andholders 68, is low,

I think the above statement as to speed, is conservative,

In this connection it must also be remembered that air cylinders may be applied to both ends of the knife holders 68 by a slight-changdin design, and that also, half the movable knives 16 may be placed on each of the drums l4 and I5, and thus allow more space for larger cylinders 85.

Since the control chains I and associated parts operate at low speeds, they may be run much faster.

It is true that the pitch line speed of the gears 25, 32, and 33, and the drive pinion 259 is high,

at a bar speed of 3000 ft. per minute; however .these high bar speedsare probably impractical except for thin material, say or less in thick- 5 ness, and in no case, with ample gear WidKt-h will there beany excessive tooth load on the gears.

It is also appropriate to point out here, that while the main incentive to the present invention was to produce a super high speed shear, the machine is equally well adapted for lower speeds.

Regarding the compressed air supply for the cylinders 85, it will be advisable to provide a separate small automatic motor driven air compressor to supply this air, both because the required pressure will be higher than the usual pressure available at the mills, and also to provide a self-contained and more reliable system.

As dust or foreign matter in the air supply could easily impair the air valves H and I20, I prefer to use a closed air system to exclude dirt and to retain lubricating oil, as shown in diagrammatic form in Fig. 17.

The motor 300 drives the compressor 30 I', which is preferably of the two stage type, and provided with an intercooler 302. The compressed air is led to a tank 304 provided with a safety valve 305. A pipe 306 leads to the supply valve I23, and the air exhausted from the cylinders 85 is returned through a pipe 30F to a larger tank 308, which is provided with a spring check valve 309, which admits air through a strainer 3? when the pressure in the tank 308 falls to about two pounds below atmospheric pressure.

The pressure tank 304 should be placed close to-the shear, and preferably, both tanks should be underground.

With this arrangement the air supplied to cylinders 85 is mostly used over and over again, and kept clean, and charged with an oil spray acquired from the'compressor cylinders, which also serves to lubricate the valves H5 and I20,

and the cylinders 85.

Air for the pinch roll cylinders 209 (in pairs) is supplied through pipes 3I I, 3I2, and 3I3, and controlled by three-way valves 3I4 and 3I5, one for each stand of rolls so that either stand may be cut out of, or into action at will.

In the foregoing description I have assumed a range of cut lengths from ft. to 30 ft. inclusive. It can now be seen that synchronous cuts of any length from one foot to 100 feet can be made, varying in length by one foot, by merely providing the appropriate control chain I95 for each of the said lengths.

It will also be apparent that as the apparatus shown is also adapted for much. lower speeds, that fewer knives can be used at such lower speeds, and this, combined with a greater percentage of asynchronism, on account of the lessened shock to the mechanism at lower speeds.

We can thus probably obtain a simpler machine on such lines, with the facility for making a complete-assortment of asynchronous cuts, or in other words, the ability to cut off any lengths of sections by variations as small as desired.

It is to be noted, that while for illustration, the rotative speed of the shear drums I4 and I5 has been describedas 300 R. P. M., the actual speed would be determined by the delivery speed of the mill, and the percentage of asynchronism used. In all cases the shear speed would automatically suit itself to the lineal delivery speed of the bar to be cut, and also to variations of this speed during the cutting cycle of a single bar.

Since accurate control of the speed of the bar 2I0 is lost when the rear end of the bar emerges from the pinch rolls 210 or 280 (whichever set is in use), I have indicated in dotted lines in Fig. l a pair of pinch rolls 252 and 253 the latter timed relation to the speed of the drums I l and I5 (preferably at a slightly higher speed to allow for slippage), the last section of the bar will be fed through the shear and cut off to approximately the same length (preferably slightly longer) as the previously cut sections. I As the upper drum I5 is mounted to float end- .wise in its hearings in order to center the helical I drive gears on the drums I4, and I5, the spring I03 for the distributing valve II5 (see Fig. 5) will produce an unbalanced force against the upper drum I5. In order to balance this force I provide, as shown in Fig. 6, a duplicate spring 33I, or at least one of equal tension, mounted in a shell 332, which may fit a counterbore in the'end of the trunnion 30, and at the opposite end of the drum I5.

A clamp 334 is secured by bolts 335 to the cover plate 336 of the bearing box 5, and a ball thrust bearing 33? is set in the shell 332, the spring 33I being placed between the bearing 33? and the clamp 334, as shown.

In Figs.' 18 and 19 I have shown suitable details for the control chains I05. These chains are of the type known as "steel thimble roller chains, and are the kind used for accurate machine drives. They have continuous offset links, and are detachable at every link, so they may be readily made up in odd or even pitch lengths.

The standard chain consists of side links 340, pins 3, shouldered bushings 342, roller 343,

and cotter pins 344. To adapt such chains for use as control chains I95, it is necessary to provide spaced special links 345, having upward projections 346, to each pair of which projections is attached a shouldered pin.34'| having an enlarged middle portion 348, which may engage the roller 20'! on lever 206.

Referring now to Fig. 1, the whole shearing and piling operation may be visualized. The mill 3I'9 delivers the bar 2I0 to the approach table 320, which carries it to the pinch rolls 280. A short table 32I bridges the gap to the pinch rolls 210, and a second short table 322 carries the bar 2I0 to the shear 255.-

This table 322 is preferably made with its upper surface slightly convex, that is, its middle roller would be /2" to 1" higher than its end rollers.

If a chute instead of a roller table is used,

' a similar effect is desirable. When making synchronous cuts this effect is not necessary, as the knives and the bar are travelling at exactly equal speeds, but when making asynchronous cuts, the bar 2I0, according to the present invention, and as previously described,will be travelling at a speed (assumed) 5% to 10% greater than that of the knives and". A glance at Fig. 7 will show, that under these conditions, the upper knife 10 will exert a slight retarding effect on the bar 2I0, tending to make it form an incipient loop. This action will occur from the time the knives 50 and I0 grip the bar 2I0 in advance ofthe position shown, until the upper knife I0 clears it, beyond the position shown (rotatively) On thin material such as we are considerin 

